In connection with a device moving in a fluid, there arises during the movement through the fluid, thus perhaps in connection with a flying machine during flight, a deformation of the fluid dynamically effective surface, thus of the lifting surface of the flying machine. This deformation is variable or changeable and depends on the effective aerodynamic forces and the inertial and/or mass forces. These are dependent on the flight condition (speed, altitude), as well as on the loading condition (useful payload, fuel quantity, position of center of gravity). Without special measures, a wing can only be designed so that it comprises the deformation that is most advantageous for the aerodynamic resistance or drag only for a single condition and time point of a flight. A different deformation, which is not drag-minimal, arises for every other condition and for every other time point.
In the state of the art, no systems have previously become known, with which the structural deformation of wings can be adapted or matched to a form or shape that is optimal for the aerodynamic resistance or drag. The influence of the structural deformation was either neglected or disregarded, simply put up with, or in the best case taken into consideration such that the deformation that is most advantageous for the aerodynamic drag arises for an “average” flight condition (average loading, half flight time).
While, of course, control surfaces that are per se adjustable are known on such fluid dynamically effective surfaces such as the lifting surface of a flying machine, these, however, serve for the control of the flight attitude or the trimming of the aircraft, but not, however, a change or variation of the deformation of the wing in the sense of an adaptation or matching to the form that is most advantageous for the aerodynamic drag dependent on the flight and loading condition. It is also known, to use conventional control surfaces on the wing trailing edge (aileron) for influencing the aerodynamic pressure distribution for a smaller structural loading (load reduction), a similar control surface concept has also become known for improving the roll control for an experimental version of a combat aircraft, similarly also for the same purpose the additional use of flaps along the wing leading edge.
The aerodynamic pressure distribution and the structural loading change or vary due to differing flight conditions (altitude, speed) and loading conditions (useful payload, fuel, position of center of gravity), whereby different elastic deformations arise. This deformation condition influences the aerodynamic (lift induced) resistance. For a given span, and without consideration of the structural loading, the minimal resistance arises for an elliptical aerodynamic pressure distribution over the span. This can be achieved through an elliptical wing plan form or through a corresponding torsion or twisting of the wing profile chord in the span direction relative to the direction of incident flow or relative wind. A wing torsion deformation in the span direction (twisting) as well as a bending deformation on the swept-back wing influence this distribution. Therefore, the drag-minimizing deformation condition can only prevail for a short time during the total duration of a flight, in which the fuel quantity changes and the flying proceeds with different speeds at different altitudes. Moreover, the magnitude of the deformation is dependent on the loading condition.